Nov 5-9, 2006 IAEA meeting, Vienna, Austria 1 Target and Chamber Technologies for Direct-Drive Laser-IFE Presented by A. René Raffray Scientific Investigators: M. Tillack, R. Raffray, F. Najmabadi University of California, San Diego 1st RCM of the CRP on Pathways to Energy from Inertial Fusion - an Integrated Approach IAEA Headquarters Vienna November 5-9, 2006

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 2 Electricity Generator Target factory Modular Laser Array Modular, separable parts: lowers cost of development AND improvements Conceptually simple: spherical targets, passive chambers Builds on significant progress in US Inertial Confinement Fusion Program Proposed Work Within Context of High Average Power Laser (HAPL) Program Target injection (engagement and surviva) Chamber conditions (physics) Final optics (+ mirror steering) Blanket (make the most of MFE design and R&D info) System (including power cycle) Dry wall chamber (armor must accommodate ion+photon threat and provide required lifetime) Multi-institution Activities led by NRL with the Goal of Developing a New Energy Source: IFE Based on Lasers, Direct Drive Targets and Solid Wall Chambers

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 3 Proposed Research (as part of HAPL Program) a) Target engagement. We will develop and demonstrate systems to track direct-drive targets in flight and to steer multiple driver beamlets onto the targets with the precision required for target ignition. Bench-top experiments will be performed in order to demonstrate the feasibility of these systems and to characterize their performance. b) Chamber design studies. We will develop chamber design concepts that integrate armor and structural material choices with a blanket concept providing attractive features of design simplicity, fabrication, maintainability, safety and performance (when coupled to a power cycle). Advanced concepts (including magnetic intervention) that could result in smaller less costly chambers, better armor survival and lower cost of electricity also will be investigated. c) Chamber armor thermomechanics. We will perform modeling and experiments on candidate chamber armor materials. The goal of this work is to develop solid armors capable of withstanding cyclic thermomechanical loading expected in direct-drive IFE chambers.

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 4 Target Engagement

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 5 Year 1: Utilize lab-scale injection equipment to support the development of target engagement methods. Field and test individual elements, including Poisson spot detection, Doppler fringe counting, glint alignment, fast mirror steering and real-time software integration. Year 2: Combine benchtop systems and extend performance. Year 3: Perform integrated demonstration of target engagement. Install all engagement systems on a prototype injector using full-speed electronics, full-power light sources and full-aperture optics. Proposed Work Plan for: a) Target Engagement

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 6 Target engagement research is performed in collaboration with General Atomics L. Carlson 1, M. Tillack 1, T. Lorentz 1, J. Spalding 1 N. Alexander 2, G. Flint 2, D. Goodin 2, R. Petzoldt 2 ( 1 UCSD, 2 General Atomics) Power plant requirements: 20 µm engagement accuracy in (x,y,z) ~20 m standoff to final optic 5-10 Hz rep rate Purpose: To individually demonstrate successful table-top experiments of key elements, then integrate together. Final goal: Provide a “hit-on-the-fly” target engagement demo meeting accuracy requirements.

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 7 Benchtop experiments simulate all of the key elements of a power plant engagement system Poisson spot, fringe counting, crossing sensors, verification: –Provide in-flight steering instructions & diagnostic, backup. Glint & coincidence sensor: –Aligns beamlets & provides final steering instructions R. Petzoldt, et al., "A Continuous, In-Chamber Target Tracking and Engagement Approach for Laser Fusion," 17th ANS Topical Meeting, to be published in Fusion Science and Technology

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 8 Goal is to know centroid position to ± 5 µm every 5 ms Looks achievable #1.Transverse target motion is tracked using Poisson spot centroiding 2) Brightness/contrast adjustment ~1 ms 1) Capture image ~1 ms 3) Threshold pixels above a certain value ~4 ms 4) Remove border objects ~2 ms 6) X,Y centroid computed with < 5 µm error (1  ) ~1 ms 5) Particle filter ~1 ms

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 9 A Michelson interferometer is used, with noise mitigation, signal processing and modifications for plane/spherical wave mixing. #2.Fringe counting provides continuous z-axis tracking, with accuracy goal of ~1 part in 10 6 Fringe count repeatability over 5  m using a 4-mm steel sphere So far, operation is limited in range and standoff (power, noise, bandwidth, …) May predict velocity (vs. full z-axis tracking)

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 10 #3.Crossing sensors initiate fringe counting and may be sufficiently accurate to supplant the interferometer C1 C2 C New real-time operating system reports on-the-fly placement repeatability of 45 µm (1  ) at C3. => Sufficiently precise to trigger glint laser Sphere dropping mechanism

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 11 micro lens array collimating lens simulated driver beam #4.To demonstrate successful engagement, we developed a high-precision verification system target eclipses verification beamlets (Diffraction- limited beamlet waist ~75 µm) 1 µm precision when the target is within the 4 beamlets

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 12 #5.The glint system provides final position update and closes the beam steering loop Optics In Motion FSM Stationary demo performed with 18 µm accuracy in 8 ms Full demonstration in progress 1)Fast steering mirror keeps alignment beam centered in the coincidence sensor. 2)Glint return provides error between alignment beam & actual target position 1-2 ms before chamber center. 3)Error signal provides final correction to FSM ns

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 13 Time sequence of tracking & engagement demo - START

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Nov 5-9, 2006 IAEA meeting, Vienna, Austria 23 Time sequence - END

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 24 Chamber Design Studies

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 25 Year 1: Perform initial scoping studies of advanced chamber options (including blanket and armor). Possible design scenarios range from large chambers without a protective chamber gas to smaller chambers with magnetic intervention. Studies include concept development and sufficient scoping design analysis to allow for a reasonable assessment of each concept based on key criteria including performance (when coupled to a power cycle), lifetime, fabrication, safety and maintenance. Year 2: Conclude scoping studies and perform assessment and comparison of different chamber options to converge on the most attractive concept(s). Develop possible design solutions for ion dumps in the case of magnetic intervention. Year 3: Perform detailed design analysis of preferred concept(s) including more detailed study of chamber integration (blanket, armor and ion dumps as required in the case of magnetic intervention) and design interfaces (ancillary coolant, power cycle and assembly & maintenance requirements). Proposed Work Plan for: c) Chamber Design Studies

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 26 Design and Analysis Based on 350 MJ-Class Baseline Direct-Drive Target Spectra Energy partition: -Neutron ~75% -Ions ~24% -X-rays ~1%

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 27 Energy Deposition Profile in W, SiC and C Armor for 350 MJ-Class Baseline Target Spectra Spectra in a m Chamber Target micro- explosion Chamber wall X-rays Fast & debris ions Neutrons Lifetime is a key issue for armor -High T and dT/dx -Ion implantation (in particular He)

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 28 Ion Power Deposition Profile in W Armor Time of flight effect due to energy range of ions Calculation based on 0.1  s time increment Fast ions Debris ions

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 29 Temperature History and Gradient for W Armor in a m Chamber Subject to the 350 MJ-Class Baseline Target Threat Spectra 1-mm W on 3.5 mm FS at 580 °C No chamber gas Peak temperature ~2400°C 1 mm thick W armor Coolant at 580°C 3.5 mm thick FS Wall Energy Front h= 10 kW/m 2 -K

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 30 Required P Xe as a Function of Yield to Maintain T W,max <2400°C for 1800 MW Fusion Power and Different R chamber Armor Survival Constraints Impact the Overall IFE Chamber Design and Operation W temperature limit of 2400°C assumed for illustration purposes (~1.2 J/cm 2 roughening threshold from RHEPP results) Limit to be revisited as R&D data become available Example chamber parameters for 0 gas pressure: -Yield = 350 MJ; R=10.5 m; Rep. rate ~ 5 for 1750 MW fusion Desirable to avoid protective chamber gas based on target survival and injection considerations Large chamber for W survival Other advanced concepts for more compact chamber and armor survival, e.g. - Magnetic intervention -Phase change armor

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 31 Self-Cooled Li Blanket for Large Chamber The design is based on an annular geometry with a first Li pass cooling the walls of the box and a slow second pass flowing back through the large inner channel. Large chamber size led to the division of blanket modules in two (upper and lower halves). Inner Li Channel Annular Li Channel Sandwich insulator: FS-SiC-FS

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 32 Self-Cooled Li Blanket Coupled to Brayton Cycle through a Heat Exchanger Example results for regular FS (T max <550°C) and ODS FS (T max <700°C)

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 33 Advanced Chamber Based on Magnetic Intervention Concept Using Cusp Coils Use of resistive wall (e,g SiC) in blanket to dissipate magnetic energy (~70% of ion energy can be dissipated in the walls). Dump plates to accommodate all ions but at much reduced energy (~30%). Dump plates could be replaced more frequently than blanket. Chamber/blanket study underway: -SiC f /SiC as structural material -Pb-17Li and flibe as breeder/coolant - Other?

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 34 It Could Be More Advantageous to Position Dump Plate In Separate Smaller Chamber Could use W dry wall dump, but would require large surface area and same problem with thermomechanical response and He implantation Could allow melting (W or low MP material in W) Hybrid case Dry wall chamber to satisfy target and laser requirements Separate wetted wall chamber to accommodate ions and provide long life Have to make sure no unacceptable contamination of main chamber Ion Dump Ring Chamber

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 35 b) Chamber armor thermomechanics

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 36 Year 1: Perform armor thermomechanics simulations experiments for a range of laser energy (peak sample temperature) and a variety of shot rates (10 to 10 5 ) for powder metallurgy tungsten samples. Year 2: Perform armor thermomechanics experiments on different candidate armor material such as single-crystal tungsten. Year 3: Perform armor thermomechanics experiments on candidate armor material bonded to candidate first wall material (e.g., tungsten bonded to ferritic steels). Proposed Work Plan for: b) Chamber armor thermomechanics

Nov 5-9, 2006 IAEA meeting, Vienna, Austria Chamber Armor Thermomechanics Experiments: Dragonfire Laser Facility F. Najmabadi, J. Pulsifer UC San Diego Objective: Develop and field simulation experiments of the thermo-mechanical response of the first wall armor of an IFE chamber to target fusion yield. Description: A laser generates on the test specimen similar surface temperature and temperature gradients found in an IFE chamber wall (e.g. YAG laser with a rep rate of 10 Hz). Surface temperature as well as mass ejecta from the specimen is measured in- situ and in real time. Material response of specimen is determined after laser exposure by a variety of microscopy techniques. Objective: Develop and field simulation experiments of the thermo-mechanical response of the first wall armor of an IFE chamber to target fusion yield. Description: A laser generates on the test specimen similar surface temperature and temperature gradients found in an IFE chamber wall (e.g. YAG laser with a rep rate of 10 Hz). Surface temperature as well as mass ejecta from the specimen is measured in- situ and in real time. Material response of specimen is determined after laser exposure by a variety of microscopy techniques.

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 38 Facility Description In-situ microscopy <25  m resolution large standoff K2 Infinity optics translator electronics Sample heater 500˚C base temperature Optical thermometer collector Sample manipulator xy translation external control located close to window INSIDE VACUUM: OUTSIDE VACUUM:

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 39 Optical thermometer measures surface temperature while QCM measures mass ejecta Sample holder at C base temperature Window allows both IR and UV lasers Quartz Crystal Microbalance (QCM) for measuring ejecta.

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 40 In-situ microscopy allows us to monitor microstructure evolution during testing Basler camera and K2 Infinity microscope – 1280x1024 resolution –25 fps –STD objective (higher mag available) USAF resolution target: - 64 line pairs/mm - 16  m resolution

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 41 Some results with powder metallurgy tungsten: Sample behavior changes at ~2,500K Room Temperature Sample 500 o C Sample   5% Error size

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 42 Damage appears at 2,500K (not correlated with  T) 12A, 100mJ, 773K, Max: 2,200K (~1,400K  T) 14A, 150mJ, RT, Max: 2,500K (~2,200K  T) 11A, 200mJ, 773K, Max: 3,000K (~2,200K  T) 15A, 150mJ, 773K, Max: 2,700K (~1,900K  T)

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 43 Effects of Shot Count and Temperature Rise 10 3 shots 10 5 shots 10 4 shots 15A, 150mJ, 773, Max: 2,700K (~1,900K  T) 14A, 150mJ, RT, Max: 2,500K (~2,200K  T)

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 44 Effects of Shot Count and Temperature Rise 10 3 shots 10 5 shots 10 4 shots 14A, 150mJ, RT, Max: 2,500K (~2,200K  T) 11A, 200mJ, 773K, Max: 3,000K (~2,200K  T)

Nov 5-9, 2006 IAEA meeting, Vienna, Austria 45 Summary of Possible Collaborative Areas of Interest Target engagement Chamber armor material development and testing Advanced chamber/blanket design study Power plant studies